There is currently an interest for the development of portable, lightweight and non-invasive biosignal activity measurement systems for monitoring biosignals and more specifically the neurophysiological activity of subjects in operational, clinical and research environments. For example, the simultaneous use of electroencephalographic (EEG) acquisition with functional near infrared spectroscopy (fNIRS) can provide a better understanding of the mechanisms involved in cerebral activation, since such techniques provide complementary information from the brain in terms of temporal and spatial resolution.
U.S. Patent Application 2014/0018640 A1, for example, describes a holder set and a brain function measuring device capable of executing measurements by an optical bioinstrumentation device (e.g. fNIRS) and by a an electroencephalograph (EEG) at the same time.
Report document “Concurrent EEG and NIRS tomographic imaging based on wearable electro-optodes”, by Tzyy-Ping Jung et al., University of California—San Diego La Jolla, Apr. 13, 2014, describes a dual-modality neuroimaging system with EEG/NIRS electrodes, known as electro-optodes, that allow non-invasive and non-intrusive acquisition of EEG and fNIR signals. The developed brain activity sensor combines the capability of simultaneously recording both EEG and fNIRS signals from the same site by integrating both EEG electrode and NIR probe into one electro-optode.